Drill and blast method in mining industry is required in hard rock strata and excavation machinery can be deployed.

As a rule, for excavation lengths longer than 4.5 km, a TBM is often recommended, while for lengths not exceeding 1.5 km, the Drill & Blast technique is usually the go-to.

Bear in mind that this rule is not set in stone. You may need very welcome across a 5 km tunnel being excavated using Drill & Blast and a 1 km tunnel being excavated using TBM, which is why each case much be studied individually.

For tunnels with excavation lengths between 1.5 km and 4.5 km, costs are comparable. So other factors must be taken into account: those relating to geology, geometry, the environment, and project timelines.

Dear Farshad,

I know those facts, I think you did not understand the question. I am asking about general or local utilization ratios.

No full answer here either. But I recall being told by a senior mining consultant that the five principal mining countries in the world D and B'd 3,500km (of therefore single-shell, some B, some S, some S(mr) some S(fr) tunnels EACH MONTH. In Norway a very rough total at present, with rounding, is 6000km D+B and 300km of TBM. Year-by-year variation of the ratio can be large in 'good TBM years' as for the past 5 years in Norway.

Dear Nick,

Thanks for your response.

Serdar! Did not see it was you until too late. Hope all is well. Nick

No Problem! That is my fault, I have not written you for a long time. Everything is in a good course. I started working at TU Bergakademie Freiberg-Germany as Research Associate. I am no more in Turkey. We have a project on intelligent sensor systems for the mechanical cutting. I hope everything is well with you and you finished your latest book.

Serdar.

Hi Serdar! Interesting changes. Hope you still get to test your shear-strength idea.

(Now three books in mind, one more complete, one in the mind only. Need longer life. Training for that!)

Hi Nick,

I still keep that in mind but I could not find the opportunity to invest time in that due to many reasons. But actually, it was a good idea and maybe in the future, we can return that again.

You are young at heart. Hope you finish all of them!

The use of TBM's in mining is almost nonexistent. For one the mobilization time is too long to move the equipment to another heading. Plus in mining, you don't have too many long straight tunnels where can use the TBM. The usage of roadheaders is also very limited in hard rock mining. In Canada, I know only a handful of projects where the roadheaders have been used. On the other hand in softrock mining such as coal or potash, the excavation of drifts is done almost exclusively by continuous miners.

A sort-of-correction is needed to the above re TBM in mining. Of course very small, but not quite 'almost non-existent' - specifically because of some prominent decline-access ramps by TBM, in Australia in particular. I also recall a horizontal and very deep 5km TBM in Chile to access mineral reserves through the Andes, where Qtbm was used for prognosis. There was even deep core available because of interest in the grades. A long time ago an under-powered TBM was tested in Lucky Friday mine in Idaho - in quartzites at > 2km depth, and with PR as low as 0.1m/hr was of course abandoned.

There are some TBMs in mining projects (I personally I have participated in pre-feasibility studies and it is becoming a more interesting/feasible excavation method in mining access and developments). What to say in Stillwater mine, used for many years now!

According to the following paper, around 100 TBMs have been used in mining projects (2016) but those are already published, it might be presumed a few more. Obviously, if we compare with civil tunnels, the difference is significant.

TUST-Challengesandopportunitiesofusingtunnelboringmachinesinmining.pdf

I agree with Nick and Javier. According to the best of my knowledge, we cannot say almost non-existent. The review paper that Javier suggested is a good example of this. And for my understanding, mechanical excavation does not mean only TBM excavation technology, that is the classification used by ITA-AITES.

Dear Serdar,

I agree with previous comments of Derek, Javier, and obviously Mr Barton, a worldwide expert about the topics.

I try to resume some useful references.

Regarding TBM, please check my MSc Thesis, it provides you a wide overview of different models used to predict utilization factor of rock TBM, as a function of the characteristics of the database (geology, geomechanics, TMB geometry) they have been created with. Really important aspect that sometimes is not considered carefully.

Regarding D&B, please check the literature provided by NTNU Trondheim, above all Zare and Bruland, it is an excellent starting point.

Hope to be an help for you.

Best Regards

Gabriele Brino

Tunnel Boring Machine is safe in weak, fractured strata with lining is suggested, in place of drilling, blasting, in case of road or railway tunnel.

Leonid Bachurin

Gabriele Brino! Enjoyed looking through your comprehensive TBM MSc. Also to see my deceleration gradient m as equations. You seem - by the language used - to be a little in doubt about Qtbm. Please see my more recent articles like 2013, and the current 2021 ISRM 4th NB on-line lecture - with updated prognoses. The time-dependence of utilization in tough projects is 'alpha-omega' - and we even see it in (most of Robbins) world records.

Gabriele Brino thanks for the suggestion. But you caught the wrong aspect by some of our previous colleagues. I need references just as Leonid proposed, not MUT numbers.

A real pleasure to know you have had a look into my thesis, Prof. Nick Ryland Barton! I will certain have a deeper look to your updated model, I often use different models in my daytime professional work, so I will go deep in it. Happy to have given some suggestions to you Serdar Yaşar, even if not asked to your question, indeed interesting work the one proposed by Leonid Bachurin